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| PhD Dissertation completed at the Institute of Advanced Material Study, Kyushu University, Japan, 1988 | ||||||||||||
| NATURAL CONVECTION IN OPEN-ENDED VERTICAL STRUCTURES CONSISTING DUCTS AND RECTANGULAR SPACE | ||||||||||||
| Flow rate characteristics of buoyancy-induced airflows in three different structures, namely, a fully-heated vertical duct, a partly-heated and partly-cooled vertical duct, and a combination of a cubic box and vertical ducts, were studied.� A simple theory for predicting the flow rate inside these structures based on buoyancy and flow resistance balance is proposed and validated by experiments.� The theory is also compared with the currently accepted two-dimensional numerical solution by finite difference for the case of a fully heated vertical duct.� The comparison shows that the simple model can accurately predict flow rates even for situations where the flow remains developing up to the duct exit.� The factors affecting the flow rate, such as the flow development in the hydrodynamic entrance region, the dependence of fluid properties on fluid temperature, and the effects of thermal stratification of ambient air, are clarified.� The corresponding heat transfer characteristics are also reported. | ||||||||||||
| M. Eng Thesis completed at the Institute of Advance Material Study, Kyushu University, Japan, 1985 | ||||||||||||
| NATURAL CONVECTION IN VERTICAL CIRCULAR TUBE | ||||||||||||
| A simple theory for predicting the natural convective flow rate inside a fully heated or a partly heated and partly cooled vertical tube is proposed.� The theory assumes that the flow inside the tube has a temperature profile that is thermally developing and a velocity profile that is �hydro-dynamically developed.� This assumption allows us to use the Graetz solution for forced convection in the computations of total buoyancy and total flow resistance;� thus simplifying �the natural convective flow rate inside the tube.� Flow rates predicted by the proposed theory are compared with values measured using a quartz fiber anemometer,� -an instrument specially developed for the study.� The agreement between theoretical and measured values is good when pressure losses at the tube inlet and exit as well as in the hydrodynamic development region are considered.� The values of pressure loss coefficient used in the computations were taken from literature for forced convection. | ||||||||||||